cibyl - an open-source
C-to-Java bytecode translator by Simon Kagstrom that I have
made a few contributions to.

Meir Tsvi has developed an interesting experimental
fork of cibyl that does C-to-MSIL bytecode
translation, for cases where porting to C# or "managed C"
is not an option for creating Windows Phone 7 apps (such
as the Waze
crowd-sourced navigation app)